1. The problem statement, all variables and given/known data heres the equation: http://img255.imageshack.us/img255/1669/untitledfa5.jpg [Broken] 2. Relevant equations i think we use cos(x) 3. The attempt at a solution i know that cos(x) = cos(pi) so the limit is -1? whats the sum, i'm a bit confused. must be in simplest form what must i show. help.